This invention relates to a cover member for an illuminated push button switch which is used for a data input unit for a mobile communication equipment, a switch unit therefor or the like, and more particularly to a cover member wherein hard resin is applied onto a top surface of key tops to improve the touch with fingers and a method for manufacturing the same.
In a mobile communication equipment, an illuminated data input unit such as an illuminated push button switch has been used in order to meet the convenience of a night service. In general, such a data input unit is so constructed that press members are mounted directly on a circuit board which is provided thereon with fixed contacts, LEDs and the like. Also, the unit includes a cover member including a substrate made of an elastomeric rubber material and provided with a plurality of movable sections. The movable sections of the substrate each are provided on a front surface thereof with a key top and a rear surface thereof a movable contact.
Such a conventional cover member as described above is typically disclosed in Japanese Patent Laid-open Publication No. 5-83347. In the cover member disclosed in the patent, key tops each are made of a hard resin material and formed on a rear surface thereof with a punched character printed layer and a colored light-permeable printed layer. Also, the cover member includes key pads each made of a silicone rubber material and including an operation section and a non-operation section. The key pads each are bonded on a surface of the operation section thereof to each of the key tops.
In the cover member disclosed in the patent, it is considered that the key tops each are formed by charging a liquid resin composition in a die and heating it without applying a pressure thereto, to thereby cure it. Thus, the conventional cover member substantially fails to render a top or upper surface of each of the key tops flat, resulting in printing of the punched character printed layer and light-permeable printed layer being highly difficult, so that a display section fails to provide distinct display.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a cover member for an illuminated push button switch which is capable of providing the hard touch with fingers when it is incorporated in a switch unit or the like.
It is another object of the present invention to provide a cover member for an illuminated push button switch which is capable of facilitating formation of a symbol/character display section exhibiting distinct display and aesthetic properties.
It is a further object of the present invention to provide a method for manufacturing a cover member for an illuminated push button switch which is capable of manufacturing a cover member accomplishing the above-described objects.
In accordance with a first aspect of the present invention, a cover member for an illuminated push button switch is provided. The cover member includes a substrate made of a light-permeable elastomeric rubber material and including a plurality of movable sections, as well as key tops arranged on the movable sections of the substrate, respectively. The key tops each include a rubber section made of a light-permeable elastomeric rubber material and a resin section made of a light-permeable hard resin material. The rubber sections each are fixed on a surface of each of the movable sections of the substrate and provided on a surface thereof fixed to the movable section with a display section. The resin sections each are fixed on a surface of the rubber section opposite to the surface thereof on which the display section is formed.
In a preferred embodiment of the present invention, the rubber sections fixed on the resin sections each include a flange arranged so as to radially outwardly extend from a lower end of an outer periphery of the resin section.
In a preferred embodiment of the present invention, the rubber sections each have hardness set between hardness of the substrate and that of the resin section.
In accordance with a second aspect of the present invention, a method for manufacturing a cover member for an illuminated push button switch is provided. The method includes the steps of pouring a flowable light-permeable hard resin composition into forming recesses of a forming die, curing the light-permeable hard resin composition in the forming recesses to form resin sections, pouring a flowable light-permeable rubber composition onto the resin sections in the forming recesses, curing the light-permeable rubber composition to form rubber sections of which one surface is fixed to the resin sections, respectively, forming a display section on the other surface of each of the rubber sections, forming a light-permeable rubber composition into a substrate including a plurality of movable sections, and bonding an upper surface of each of the movable sections of the substrate and the other surface of each of the rubber sections on which the display section is formed to each other by means of an adhesive.
In a preferred embodiment of the present invention, the display section is formed by providing a light-shielding colored layer formed with a symbol/character-like punched hole on the one surface of each of the rubber sections and charging a light-permeable colored layer onto the light-shielding colored layer in the punched hole.
Also, in accordance with the first aspect of the present invention, a cover member for an illuminated push button switch is provided. The cover member includes a substrate made of a light-permeable elastomeric rubber material and including a plurality of movable sections, as well as key tops arranged on the movable sections of the substrate, respectively. The key tops each include a rubber section made of a light-permeable elastomeric rubber material and a resin section made of a light-permable hard resin material. The rubber section has a flat surface through which the rubber section is fixed on a surface of each of the movable sections of the substrate and provided on the flat surface thereof fixed onto the movable section with a display section. The resin section is fixed on a surface of the rubber section opposite to the flat surface thereof on which the display section is formed. The substrate, rubber section and resin section are made so as to have Shore A hardness of 30 to 65, Shore A hardness of 60 to 80 and Shore D hardness of 50 to 80, respectively.
In a preferred embodiment of the present invention, the rubber section fixed on the resin section includes a flange arranged so as to radially outwardly extend from a lower end of an outer periphery of the resin section.
Further, in accordance with the second aspect of the present invention, a method for manufacturing a cover member for an illuminated push button switch is provided. The method includes the steps of pouring a flowable light-permeable hard resin composition into forming recesses of a forming die, curing the light-permeable hard resin composition in the forming recesses while heating it without applying a pressure thereto, to thereby form resin sections, pouring a flowable light-permeable rubber composition onto the resin sections in the forming recesses, curing the light-permeable rubber composition while heating and pressurizing it, to thereby form rubber sections of which one surface is fixed to the resin sections, respectively, forming the other surface of each of the rubber sections into a flat surface, forming a display section on the flat surface of each of the rubber sections by a screen printing means, forming a light-permeable rubber composition into a substrate including a plurality of movable sections, and bonding an upper surface of each of the movable sections of the substrate and the flat surface of each of the rubber sections to each other by means of a light-permeable adhesive.
Moreover, in accordance with this aspect of the present invention, a method for manufacturing a cover member for an illuminated push button switch is provided. The method includes the steps of charging a hard resin composition in forming recesses of a forming die, curing the composition without applying a pressure thereto to form resin sections of 50 to 80 in Shore D hardness, placing a rubber composition on the resin sections while keeping the resin sections in the forming recesses, subjecting the rubber composition to pressurizing and heating by means of the forming die, to thereby form rubber sections each having one surface adhered to each of the resin sections and the other surface formed into a flat surface and having 60 to 80 in Shore A hardness, resulting in providing a semi-finished product, and forming a symbol/character display section on the flat surface of each of the rubber sections while positioning and holding the semi-finished product. The symbol/character display section is constituted of a light-shielding colored layer and a light-permeable colored layer each formed by screen printing. The method also-includes the steps of subjecting a rubber composition to molding by means of a top force and a bottom force, to thereby form a substrate of 30 to 65 in Shore A hardness including a plurality of movable sections, applying a light-permeable adhesive to an upper surface of each of the movable sections of the substrate, and bonding the upper surface of each of the movable sections and the flat surface of each of the rubber sections to each other through the adhesive.
The cover member according to the present invention constructed as described above is combined with a circuit board to constitute an illuminated push button or a data input unit in cooperation with the circuit board. The circuit board is provided thereon with fixed contacts and light emitters such as LEDs or the like. The cover member includes the substrate wherein a plurality of movable sections each are contiguous to each of the base sections through a skirt section, as well as key tops respectively fixed on the movable sections of the substrate.
The substrate may be made of at least one selected from the group consisting of, for example, synthetic rubber materials such as urethane rubber, acrylic rubber, butyl rubber, silicone rubber, isoprene rubber and ethylene-propylene-diene terpolymer; natural rubber materials; light-permeable elastomeric rubber elastomers such as polyester and urethane thermoplastic elastomers; and the like. The movable sections each are provided on a rear surface thereof with a conductive movable contact in a manner to be contactable with the fixed contact on the circuit board. The substrate is formed while being heated and pressurized by means of a mold or die in a step separate from that of forming the key tops. For example, it may be formed of the above-described light-permeable rubber composition by compression molding, injection molding, injection compression molding or the like.
The key tops each include the light-permeable hard resin section, the light-permeable rubber section and a symbol/character display section formed on the rear surface of the rubber section which is a surface of the rubber section fixed to the movable section of the substrate (hereinafter also referred to xe2x80x9cfixed surfacexe2x80x9d). The rubber sections each are adhered on the rear surface or fixed surface thereof to the movable section of the substrate by means of an adhesive. The resin sections each are formed into a layer-like configuration or a block-like configuration of a considerable thickness and made of a colored or colorless light-permeable resin having Shore D hardness (durometer hardness) of 50 to 80 such as acrylic resin, methacrylate resin, polyester resin, polycarbonate resin or phenyl methyl silicone resin. The resin sections may be normally formed by charging a liquid hard resin composition formable integrally with the rubber material for the rubber sections in forming recesses of a forming die and heating it without applying a pressure thereto, to thereby cure it. The resin compositions for the resin sections which is formable integrally with the rubber material include, for example, a material which is obtained by mixing thermosetting unsaturated polyester resin with a curing agent, a vinyl monomer acting as an adhesion promoter and epoxy resin promoting both an increase in mechanical strength and shrinkage prevention, as well as a material which is obtained by mixing high-hardness silicone resin such as dimethyl phenyl silicone resin or phenyl methyl silicone resin with a vinyl monomer.
The rubber sections each may be formed into a layer-like or laminar shape and made of a rubber elastomer or elastomeric rubber material similar to that for the substrate described above and preferably the same elastomeric rubber material as that for the substrate. Alternatively, it may be made of the same elastomeric rubber material as that for the substrate which has hardness of a level between hardness of the substrate and that of the resin section, such as, for example, silicone rubber. The cover member is preferably constructed so that the resin sections, substrate and rubber sections have Shore D hardness of 50 to 80, Shore A hardness of 30 to 65 and Shore A hardness of 60 to 80, respectively. Such construction increases resistance to peeling at an interface between the resin section and the rubber section and at that between the rubber section and the substrate and improves the touch with fingers. Desirably, the rubber sections, as described above, each are formed with the flange in a manner to slightly radially outwardly extend from a lower end of an outer periphery of a body thereof. The flange prevents leakage of light from an equipment on which the cover member is mounted. In order that the flange effectively prevents leakage of light from the equipment without increasing pitches of the key tops, it preferably extends by a distance of about 0.2 to 0.5 mm from the outer periphery of the resin section. Also, in order to ensure satisfactory release during the molding and prevent a deterioration in workability in printing of the symbol/character display section, it is preferably formed into a thickness of about 0.3 to 1.0 mm. For example, it is preferably formed into a thickness identical with or smaller than that of the rubber section.
The rubber sections, as described above, each are formed by charging the above-described light-permeable rubber composition onto the resin section received in each of the forming recesses and heating it while applying a pressure thereto, resulting in being fixed to the resin section. The rubber section is cut into a predetermined shape either after formation of the symbol/character display section thereon or before the formation. Desirably, the substrate and rubber sections are made of a silicone rubber elastomer, the symbol/character display section is made of a silicone ink by printing, and a silicone adhesive is used for adhesion between the substrate and the key tops. This ensures an increase in adhesion strength and an improvement in quality.
The symbol/character sections each may be formed by arranging the light-shielding colored layer formed with the punched hole indicating a symbol or character on the fixed surface of each of the rubber sections. Alternatively, it may be formed by arranging the light-shielding colored layer as described above and laminating the light-permeable colored layer on the light-shielding colored layer. The symbol/character display section may be formed by printing the light-shielding colored layer and light-permeable colored layer. For example, it may be formed by printing the layers by means of a screen printing machine or the like while securely holding the integrally bonded rubber section and resin section by means of a holding fixture.
Fixing of each of the key tops to the substrate is carried out by fixing the symbol/character display section of the rubber section on the top surface of the movable section of the substrate by means of a light-permeable (colored transparent or colorless transparent) adhesive. The adhesion may be carried out, for example, by previously applying the adhesive to the top surface of the movable section of the substrate by screen printing or the like, positioning the key top held by the holding fixture on the movable section of the substrate while holding the substrate at a predetermined position by means of a fixing fixture, and bonding the symbol/character display section of the key top onto the top surface of the movable section. Then, the holding fixture and fixing fixture are removed from the substrate having the key top fixed thereon and then the substrate is placed in a heating oven to cure the adhesive, leading to completion of the cover member.